The present invention relates to aqueous compositions comprising at least one phenolic compound and at least one hydrotrope, for cosmetic use.
The formation of free radicals is a widely accepted pivotal mechanism leading to skin aging. Free radicals are highly reactive molecules with unpaired electrons that can directly damage various cellular membranes, lipids, proteins, RNA and DNA. The damaging effects of these reactive oxygen species are induced internally during normal metabolism and externally through various oxidative stresses. UV exposure and environmental pollution can accelerate skin aging by producing free radicals in skin. Antioxidants protect cells from the damage of oxidative stress by scavenging free radicals and inhibiting following oxidation reactions. The topical application of antioxidants is broadly used in skin care product to prevent skin aging.
Phenol/polyphenols, the most abundant antioxidants in diet, are well known as very effective anti-oxidants. They have been widely studied in the prevention of degenerative diseases, particularly cardiovascular diseases and cancers. Many phenol/polyphenols have been formulated in nutrition supplement and consumer products. However, the solubility of most phenol/polyphenols is very limited, especially in water, which diminishes their applications and biological potential in cosmetics. Thus, there is a need for methods of increasing the water solubility of phenol/polyphenols.
Applications and biological potential of many phenol/polyphenols in cosmetics are limited due to their poor solubility. Various delivery systems, such as gel carriers (US application publication 20020086042), or nano crystals (US application publication 2010/0047297), or chemical modification of the polyphenols (US application publications 20090233876, 20080095866, and 20080176956) have been used to obtain better solubility of phenol/polyphenols. However, these approaches have drawbacks. Some are tied to specific delivery systems. Modification of phenol/polyphenols increases costs, the improvement of solubility is still limited, and modifications can reduce the activity of the phenol/polyphenols.
Other solutions to the problem of poor solubility include the use of solubilizers such as strong organic solvents (U.S. Pat. No. 5,532,012) and diterpene glycosides (US application publication 2011/0033525). Nevertheless, these solutions do not have good safety, and are not necessarily compatible with cosmetic formulations. Moreover, most of the time, when water is added to such compositions, the solubility of the phenol/polyphenols decreases dramatically.
Thus, there remains a need for methods for improving the water solubility of phenolic compounds, including polyphenols, for cosmetic and other uses.